1. Field of the Invention
This invention relates to the preparation of initiators for Group Transfer Polymerization.
2. Background
U.S. Pat. Nos. 4,414,372; 4,417,034; 4,508,880; 4,524,196; 4,581,428; 4,588,795; 4,598,161; 4,605,716, 4,622,372; 4,656,233; 4,659,782; 4,659,783; 4,681,918; 4,695,607; 4,711,942; and 4,732,955; and in commonly assigned United States Patent Applications Ser. Nos. 912,117 filed Sept. 29, 1986; 934,826 filed Nov. 25, 1986; 004,831 filed Jan. 13, 1987; 007,758 filed Jan. 27, 1987; 015,727 filed Feb. 27, 1987; and 048,958 filed May 19, 1987; referred to hereinafter as "the aforesaid patents and patent applications", disclose processes for polymerizing an acrylic or maleimide monomer to a "living" polymer in the presence of:
(i) an initiator which is a tetracoordinate organosilicon, organotin or organogermanium compound having at least one initiating site; and
(ii) a co-catalyst which is a source of fluoride, bifluoride, cyanide or azide ions or a suitable Lewis acid, Lewis base or selected oxyanion. Such polymerization processes have become known in the art as Group Transfer Polymerization (Webster et al.,J. Am. Chem. Soc., 105: 5706 (1983)).
Preferred monomers for use in Group Transfer Polymerization are selected from acrylic and maleimide monomers of the formula CH.sub.2 .dbd.C(Y)X and ##STR1## and mixtures thereof, wherein:
X is --CN, --CH.dbd.CHC(O)X' or --C(O)X';
Y is --H, --CH.sub.3, --CN or --CO.sub.2 R, provided, however, when X is --CH.dbd.CHC(O)X', Y is --H or --CH.sub.3 ;
X' is --OSi(R.sup.1).sub.3, --R, --OR or --NR'R";
each R.sup.1, independently, is a hydrocarbyl radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical containing up to 20 carbon atoms or --H, provided that at least one R.sup.1 group is not --H; R is:
(a) a hydrocarbyl radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical containing up to 20 carbon atoms;
(b) a polymeric radical containing at least 20 carbon atoms;
(c) a radical of (a) or (b) containing one or more ether oxygen atoms within aliphatic segments thereof;
(d) a radical of (a), (b) or (c) containing one or more functional substituents that are unreactive under polymerizing conditions; or
(e) a radical of (a), (b), (c) or (d) containing one or more reactive substituents of the formula --Z'(O)C--C(Y.sup.1).dbd.CH.sub.2 wherein Y.sup.1 is --H or --CH.sub.3 and Z' is O or NR40 wherein R' is as defined below; and
each of R' and R" is independently selected from C.sub.1-4 alkyl.
Preferred initiators are selected from tetracoordinate organosilicon, organotin and organogermanium compounds of the formulas (Q').sub.3 MZ, (Q').sub.2 M(Z.sup.1).sub.2 and [Z.sup.1 (Q').sub.2 M].sub.2 O wherein:
each Q.sup.1, independently, is selected from R.sup.1, OR.sup.1, SR.sup.1 and N(R.sup.1).sub.2 ;
R.sup.1 is as defined above for the monomer;
Z is an activating substituent selected from the group consisting of ##STR2## --OP[OSi(R.sup.1).sub.3 ].sub.2 and mixtures thereof;
R',R", R and R.sup.1 are as defined above for the monomer;
Z.sup.1 is ##STR3##
X.sup.2 is --OSi(R.sup.1).sub.3, --R.sup.6, --OR.sup.6 or --NR'R";
R.sup.6 is
(a) a hydrocarbyl radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical containing up to 20 carbon atoms;
(b) a polymeric radical containing at least 20 carbon atoms;
(c) a radical of (a) or (b) containing one or more ether oxygen atoms within aliphatic segments thereof;
(d) a radical of (a), (b) or (c) containing one or more functional substituents that are unreactive under polymerizing conditions; or
(e) a radical of (a), (b), (c) or (d) containing one or more initiating sites; and each of R.sup.2 and R.sup.3 is independently selected from --H and hydrocarbyl, defined as for R.sup.6 above, subparagraphs (a) to (e);
R', R" and R.sup.1 are as defined above for the monomer;
Z' is as defined above for the monomer;
m is 2, 3 or 4;
n is 3, 4 or 5;
R.sup.2 and R.sup.3 taken together are ##STR4## provided Z is ##STR5## X.sup.2 and either R.sup.2 or R.sup.3 taken together are ##STR6## provided Z is ##STR7## and
M is Si, Sn, or Ge, provided, however, when Z is ##STR8##
M is Sn or Ge.
Preferred co-catalysts are selected from a source of bifluoride ions HF.sub.2.sup.-, or a source of fluoride, cyanide or azide ions, or a source of oxyanions, said oxyanions being capable of forming a conjugate acid having a pKa (DMSO) of about 5 to about 24, preferably about 6 to about 21, more preferably 8 to 18, or a suitable Lewis acid, for example, zinc chloride, bromide or iodide, boron trifluoride, an alkylaluminum oxide or an alkylaluminum chloride, or a selected Lewis base.
Additional details regarding Group Transfer Polymerization can be obtained from the aforesaid patents and patent applications, the disclosures of which are hereby incorporated by reference.
Razuvaev et al., Vysokomol.Soedin.(B), 25(2): 122-125 (1983) disclose polymerization of methyl methacrylate and/or styrene initiated by a mixture of silicon tetrachloride and alkyls of mercury, tin or lead, at 20.degree.-50.degree. C. Sakurai et al , Tetrahedron Lett., 21:2325-2328 (1980) disclose mercuric iodide catalyzed isomerization of (trimethylsilylmethyl)chloromethyl ketone to (1-chloromethyl ethenyl)oxytrimethylsilane.
Burlachenko et al., Zhur, Obshchei Khim.,43(8):1724-1732 (1973) disclose isomerization of cis-ketene silyl acetals into the trans-isomer catalyzed by triethylsilyl bromide and mercuric bromide. Litvinova et al., abstract of Dokl. Akad. Nauk SSSR, 173(3):578-580 (1967); CA 67: 32720j, disclose the mercuric iodide-catalyzed rearrangement of triethylacetonylsilane to (isopropenyloxy)triethylsilane.
Baukov et al., abstract of Dokl. Akad Nauk. SSSR, 157(1, :119-121 (1964, CA 61: 8333f, disclose the mercuric iodide-catalyzed rearrangement of [(1-methoxy-1-ethenyl)oxy]triethylsilane to methyl 2-triethylsilylacetate.
Satchell et al., Qtr. Rev. Chem Soc., 25:171 (1971) disclose that mercuric halides are very weakly acidic Lewis acids.
Saigo et al.,Chem. Letters, 2, 163 (1976) disclose the Michael-type addition of O-silylated ketene acetals to .alpha.,.beta.-unsaturated carbonyl compounds, specifically ketones and acetals, in the presence of titanium tetrachloride to form 1:1 adducts which are ketoesters.
U.S. Pat. No. 4,732,955, supra, discloses Group Transfer Polymerization of one or more acrylate or acrylamide monomers in the presence of a mercury compound of the formula R.sup.7 HgI, wherein R.sup.7 is a C.sub.1-10 hydrocarbyl radical, or HgL.sub.2, wherein L is I or ClO.sub.4. Commonly assigned United States Patent Application Ser. No. 07/176,808 filed Apr. 1, 1988 concurrently filed herewith discloses the use of these mercury compounds in admixture with a silane of the formula (R.sup.1).sub.3 Si--Z.sup.2 as catalysts in Group Transfer Polymerization. In the formula:
each R.sup.1, independently, is a hydrocarbyl radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical containing up to 20 carbon atoms or --H, provided that at least one R.sup.1 group is not --H; and
Z.sup.2 is I, Br, Cl or trifluoromethylsulfonate.
The present invention provides a process for preparing a 1:1 adduct of a silyl ketene acetal and an .alpha.,.beta.-unsaturated compound, the adduct being an active initiator in Group Transfer Polymerization, the process being catalyzed by a mercury compound or a selected Lewis acid in the presence of a selected silane promoter. There is no suggestion of such a process in any of the foregoing publications. Similar adducts have been prepared using Lewis acid catalysts alone, such as titanium halides, but these reactions require low (-78.degree. C.) temperatures and give poor yields of adduct. With the catalysts used herein, the adduct can be prepared at room temperature, frequently in quantitative yield, and the catalyst residues are readily separated from the reaction mixture.